Feb. 2, 1935: You Lie

1935: A polygraph machine (sometimes known as the “lie detector”) is used for the first time by its co-inventor to bring a conviction in court.

Criminal justice systems in many societies have long believed that you can spot a liar based on several physiological reactions to questioning. An increase in blood pressure and heart rate, dry mouth, perspiration — all are believed to suggest the likelihood of guilt. All these factors are present in someone feeling anxiety and, well, why would you feel anxiety unless you were lying?

The polygraph measures and records these reactions, but of course the method is not exactly foolproof. Some people get anxious easily and fold at the knees without any real provocation. Others are as cool under duress as the proverbial cucumber.

Nevertheless, on Feb. 2, 1935, Leonarde Keeler, a detective and co-inventor of the Keeler polygraph, tested his invention on two suspected criminals in Portage, Wisconsin. The results of these tests were admitted as evidence in court and both suspects were convicted of assault.